以 Centos7 系统为例，详细记录一下 Jenkins 搭建流程。

参考官网：https://www.jenkins.io/doc/book/installing/linux/#red-hat-centos

Install Jenkins

从 redhat-stable yum 存储库中安装 LTS（长期支持） 版本，该版本较为稳定。

sudo wget -O /etc/yum.repos.d/jenkins.repo \
    https://pkg.jenkins.io/redhat-stable/jenkins.repo
sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io.key
sudo yum upgrade
# Add required dependencies for the jenkins package
sudo yum install java-11-openjdk
# Verify 
java -version
sudo yum install jenkins
sudo systemctl daemon-reload

Start Jenkins

systemctl enable jenkins
systemctl start jenkins
systemctl status jenkins

Configuring the Jenkins platform

Unlocking Jenkins

当首次访问新的 Jenkins 实例时，系统会要求您使用自动生成的密码解锁它。

浏览到 http://localhost:8080（或在安装 Jenkins 时为它配置的任何端口）并等待解锁 Jenkins 页面出现。

在安装 Jenkins 的机器中查看  /var/lib/jenkins/secrets/initialAdminPassword 目录文件下的内容填入改框即可。  

Customizing Jenkins with plugins

解锁 Jenkins 后，会出现 Customize Jenkins 页面。作为初始设置的一部分，可以在此处安装任意数量的有用插件。

如果不确定需要什么插件，请选择安装建议的插件。您可以稍后通过 Jenkins 中的 Manage Jenkins > Plugins 页面安装（或删除）其他 Jenkins 插件。

Creating the first administrator user

 使用 admin 账号继续即可，也可以输入想创建的用户详细信息以创建新的管理员用户。

实例配置保存并完成即可。

以上，Jenkins 就安装成功可以正常使用了。

TroubeShooting

安装完成 Jenkins 后，通过 systemctl start Jenkins 启动，报错：

Job for jenkins.service failed because the control process exited with error code. See 
"systemctl status jenkins.service" and "journalctl -xe" for details.

如果直接通过 systemctl status jenkins 查看报错，报错会很模糊，找不到具体原因

[root@master init.d]# systemctl status jenkins
● jenkins.service - Jenkins Continuous Integration Server
   Loaded: loaded (/usr/lib/systemd/system/jenkins.service; disabled; vendor preset: disabled)
   Active: failed (Result: start-limit) since Tue 2023-03-21 09:56:52 CST; 35s ago
  Process: 11715 ExecStart=/usr/bin/jenkins (code=exited, status=1/FAILURE)
 Main PID: 11715 (code=exited, status=1/FAILURE)

Mar 21 09:56:52 master.cn systemd[1]: jenkins.service: main process exited, code=exited, status=1/FAILURE
Mar 21 09:56:52 master.cn systemd[1]: Failed to start Jenkins Continuous Integration Server.
Mar 21 09:56:52 master.cn systemd[1]: Unit jenkins.service entered failed state.
Mar 21 09:56:52 master.cn systemd[1]: jenkins.service failed.
Mar 21 09:56:52 master.cn systemd[1]: jenkins.service holdoff time over, scheduling restart.
Mar 21 09:56:52 master.cn systemd[1]: Stopped Jenkins Continuous Integration Server.
Mar 21 09:56:52 master.cn systemd[1]: start request repeated too quickly for jenkins.service
Mar 21 09:56:52 master.cn systemd[1]: Failed to start Jenkins Continuous Integration Server.
Mar 21 09:56:52 master.cn systemd[1]: Unit jenkins.service entered failed state.
Mar 21 09:56:52 master.cn systemd[1]: jenkins.service failed.

我们换一种启动方式查看报错，进入 /etc/init.d，通过 ./jenkins start 启动

[root@master init.d]# cd /etc/init.d

[root@master init.d]# ./jenkins restart

Starting Jenkins Running with Java 19 from /usr/lib/jvm/jdk-19-oracle-x64, which is not yet fully supported.
Run the command again with the --enable-future-java flag to enable preview support for future Java versions.
Supported Java versions are: [11, 17]

从这里能看出来，是我们安装的版本不对，支持的Java版本只有：[11，17]，所以我们需要通过 rpm -e --nodeps 强制卸载已安装的版本，安装另外的版本。

[root@master init.d]# rpm -qa|grep jdk
java-1.8.0-openjdk-1.8.0.362.b08-1.el7_9.x86_64
copy-jdk-configs-3.3-11.el7_9.noarch
jdk-19-19.0.2-7.x86_64

[root@master init.d]# rpm -e --nodeps java-1.8.0-openjdk-1.8.0.362.b08-1.el7_9.x86_64
[root@master init.d]# rpm -e --nodeps jdk-19-19.0.2-7.x86_64

 在官网找到合适版本的链接：Java Downloads | Oracle 中国

[root@master ~]# wget https://download.oracle.com/java/17/latest/jdk-17_linux-x64_bin.rpm
--2023-03-21 09:44:24--  https://download.oracle.com/java/17/latest/jdk-17_linux-x64_bin.rpm
Resolving download.oracle.com (download.oracle.com)... 23.192.208.88
Connecting to download.oracle.com (download.oracle.com)|23.192.208.88|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 181343596 (173M) [application/x-redhat-package-manager]
Saving to: ‘jdk-17_linux-x64_bin.rpm’

100%[==========================================================================================>] 181,343,596 15.2MB/s   in 13s

2023-03-21 09:44:37 (13.3 MB/s) - ‘jdk-17_linux-x64_bin.rpm’ saved [181343596/181343596]

[root@master ~]# rpm -ivh jdk-17_linux-x64_bin.rpm
warning: jdk-17_linux-x64_bin.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:jdk-17-2000:17.0.6-9             ################################# [100%]


[root@master ~]# java -version
java version "17.0.6" 2023-01-17 LTS
Java(TM) SE Runtime Environment (build 17.0.6+9-LTS-190)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.6+9-LTS-190, mixed mode, sharing)

然后在 /etc/init.d 下重新启动 Jenkins 即可

[root@master ~]# cd /etc/init.d

[root@master init.d]# ./jenkins start
Starting Jenkins Running from: /usr/share/java/jenkins.war
                                                           [  OK  ]

为 Jenkins 配置 nginx 反向代理

参考：Reverse proxy - Nginx

nginx 配置：只需在监听 80 端口的 server 块中添加一个 location 块

location /jenkins {
    proxy_pass http://127.0.0.1:8080;
    access_log /var/log/nginx/jenkins-access.log;
}

根据以上内容正常安装好 Jenkins 后，我们直接访问 http:ip:8080 即可访问到 Jenkins 网站，即 Jenkins 的根目录直接是端口，没有统一的一个目录。

而配置该 nginx 后，会将 本机 ip/jenkins 的访问代理到 http://ip:8080/jenkins 上，但我们 Jenkins 网站默认首页直接就是端口，并没有/jenkins 这个 url，所以当我们直接访问 ip/jenkins 时就会返回 404。

所以 Jenkins 控制器和反向代理必须使用相同的上下文路径，需要修改 Jenkins 的 URL，即如果 Jenkins 控制器的 URL  为https://www.example.com/jenkins/，那么 --prefix=/jenkins 参数必须包含在 jenkins 控制器命令行参数中。

通过运行 systemctl edit jenkins 并添加以下内容来设置使用 Linux 包时的上下文路径：

systemctl edit jenkins 

[Service]
Environment="JENKINS_PREFIX=/jenkins"

然后重启 Jenkins 服务，可以通过 systemctl status jenkins 查看到我们新加的内容 

这时再通过 http://ip/jenkins 访问即可正常访问~